Defective MOF-supported Poly(ethylene oxide) Composite Polymer Electrolytes for High-Performance All-Solid-State Lithium Ion Batteries

Abstract

Solid polymer electrolytes (SPEs) can effectively reduce the safety hazards associated with traditional liquid electrolytes due to their excellent thermal and mechanical stability. However, the low ionic conductivity of SPEs at room temperature and their poor interfacial stability have hindered their broader applications. Herein, we have designed and synthesized of a cyano-functional lithium salt, named Li-FBCSI, and further prepared poly(ethylene oxide) (PEO)-based polymer electrolytes composited with defective UiO-66 nanoparticles using a solution casting approach. The as-prepared defective UiO-66 nanoparticles decorated SPEs exhibit high ionic conductivity (2.19 × 10^-4 S·cm^-1 at 60°C), a wide electrochemical stabilization window (5.39 V, vs Li⁺/Li), and an improved Li⁺ transference number (0.44). On the contrary, SPEs without the use of defective UiO-66 nanoparticles as fillers exhibit an ionic conductivity of 1.03 × 10^-4 S·cm^-1 at 60°C, and the electrochemical stabilization window decreased to 5.16 V. The assembled all-solid-state LiFePO₄ battery delivered an initial discharge capacity of 130 mA·h·g^-1 at 60°C, and maintained a discharge capacity of 114.2 mA·h·g^-1 after 100 cycles. The excellent electrochemical performance of all-solid-state LiFePO₄ battery is mainly attributed to the Li-FBCSI/ PEO/UiO-66 composites, where the defective UiO-66 offers a significant number open metal sites for anchoring FBCSI anions, thereby facilitating a rapid Li⁺ transport. Our work presents a simple and effective route for preparing MOF-decorated SPEs for high-performance all-solid-state lithium-ion batteries.